The goal of this research is to uncover the neuronal mechanisms that limit the development of visual performance in primates. Recent advances in visual psychophysics and theory have made it possible to formulate questions about visual development in the same terms used to analyze adult vision, and we are conducting experiments to explore the neurobiology of development in these functional terms. The experiments in this project hinge on the measurement of visual efficiency, the fidelity with which contrast is encoded in the visual system. Contrast thresholds measured behaviorally in the presence or absence of masking noise are assessed in infant macaques as a function of age. We confirmed that, as the animals mature, visual efficiency improves with contrast sensitivity. To try to establish the underlying mechanisms we recorded from neurons in lateral geniculate nucleus (LGN) and primary visual cortex (V1) in newborns. We found that the degree of improvement in sensitivity and resolution of neurons in LGN was not substantial enough to account for the behaviorally measured changes. Our recordings in V1 are as yet quite preliminary, but we expect to find a greater degree of maturation in V1 than we found at the level of the LGN. In addition to these studies, we have begun to measure the development of sensitivity to visual motion in primates. We plan to study the maturation of visual motion processing areas in the cortex to understand the maturational processes that underlie visual motion processing in infants.